Load introducing element

ABSTRACT

A load introducing element for a control surface of an aircraft or a spacecraft comprises at least one first component, one second component and one first flange. At least one surface area of the first component is adapted to conform to the inner contour of the control surface. The second component has at least one eye for receiving bearing means for mounting the control surface. A cross sectional profile of the first component has two or more essentially straight legs, which are connected together on their upper side by an upper edge which is adapted to an upper contour of the control surface. The load introducing element is formed by a fiber reinforced composite material having an integral type of construction in which all of the components are jointly infiltrated and cured. The invention also provides a method for producing such a load introducing element, a drive armature and an aircraft that includes such a load bearing element.

BACKGROUND AND SUMMARY OF THE INVENTION

This application claims the priority of German patent document 10 2008047 793.1, filed Sep. 17, 2008, the disclosure of which is expresslyincorporated by reference herein.

The present invention relates to a load introducing element for acontrol surface of an aircraft or a spacecraft, as well as to a methodfor manufacturing the same, and to an aircraft including the same.

Larger control surfaces of commercial passenger airplanes often includeribs, which are mounted on at least one spar and are enveloped by anouter skin. Control surfaces with a relatively complex movement pattern(which, for example, goes well beyond a simple flapping) require aspecial mounting and special drive elements. Thus, for example, in orderto increase the lift coefficient in certain flight phases Fowler flapsmove in both a translatory and rotational manner and, correspondingly,are mounted in a moveable manner (for example, on pendulum supports,roller carriages or the like) and deflected by a pivotably mountedactuator.

Therefore, a control surface design which is adapted to the abovefeatures includes at least one rib that serves as the interface betweenloads that occur on the control surface and the structure of the craft.Furthermore, this rib can be used to mount the control surface.Currently such “load introducing ribs” are manufactured as a metal partto be milled—even in the case of a total CRP [carbon fiber reinforcedplastic] construction of the control surface itself—and are mechanicallyconnected to the control surface (for example, by interlockingconnecting elements).

The production of such a metal load introducing rib is very expensivebecause it involves mechanical machining of a solid workpiece and, thus,results in high costs. Furthermore, there is the drawback that in thecase of control surfaces that are made of fiber reinforced compositematerials, a metal load introducing rib has a different heat expansionbehavior than the control surface, attached to it. The result may bemechanical stresses that can be compensated only by means of suitablydesigned structures or by flexible mountings. Consequently such metalload introducing ribs are extremely disadvantageous in modern commercialpassenger airplanes with control surfaces that are made of fiberreinforced composite materials.

One object of the present invention is to provide a load introducingelement that does not suffer from the above described drawbacks; butrather is as simple as possible to produce, weighs as little aspossible, and has a heat expansion behavior that is similar to that, forexample, of a control surface that is made of a fiber reinforcedcomposite material.

This object of the invention is achieved by the load introducing elementaccording to the invention, as well as a method for manufacturing such aload introducing element, and an aircraft with at least one controlsurface and at least one such load introducing element.

According to one aspect of the invention, the inventive load introducingelement has a first component and a second component which fulfill twodifferent functions. When viewed from the shape of its upper surface,the first component acts as a conventional rib, making it possible toachieve a covering by way of the inventive load introducing element witha continuous contour. The second component has at least one eye forreceiving bearing means for mounting the control surface, so that themechanical load introduction is achieved in essence by means of thesecond component, which transfers the load into the first component thatis connected to said second component.

An additional very important aspect of the invention lies in the factthat the individual components of the inventive load introducing element(for example, the first component and the second component) are notproduced separately from each other and are not subsequently adapted toeach other and connected together in an expensive manner. Rather theindividual components, composed of one layer or multiple layers offibrous preforms, are laid and then are jointly infiltrated and cured,for example, in an appropriate mold. In this way it is possible toproduce the individual components in the form of fibrous substructurescomprising multiple layers of a fibrous perform, and then to assemblethese fibrous substructures in the mold, in order to infiltrate and curejointly the whole assembly of fibrous substructures.

According to this method, the load introducing element of the inventionexhibits very uniform material properties, and due to the jointinfiltration and curing, the individual components are also connectedtogether in an optional way to form an integral module made of fiberreinforced composite material. Similarly the individual components canbe optimized with respect to the ensuing force directions, for example,by means of suitably oriented fibers. Such an optimization could not beachieved if the components were made of metal, because such an ultralightweight member, which is optimized for force directions, cannot beproduced by machining or deformation. With mechanical processing toolsthe cost would clearly be too high, and the resulting component would betoo cost intensive.

Furthermore, the weight can be significantly reduced by manufacturingfrom a fiber reinforced composite material, comprising individualfibrous preforms and a matrix material, so that a control surface thatis equipped with a load introducing element according to the invention,can be significantly lighter than a conventional control surface with ametal load introducing rib.

Another important aspect of the invention is that the heat expansionbehavior of a whole control surface with a load introducing element ofthe invention is homogeneous, so that no structural or mechanicaladjustments are required to accommodate different heat expansionbehaviors between the control surface and the metal load introducingrib.

In a preferred embodiment of the load introducing element of theinvention, the first component has a surface area that is adapted to theinner contour of the contour surface, so that a covering can be carriedout, as in the case of all reinforcement ribs of the control surface. Across sectional profile of this first component of the preferredembodiment has two or more essentially straight legs which are connectedtogether on their upper side by means of an upper edge that is adaptedto an upper contour of the control surface. Furthermore, at least onefirst flange for connecting to at least one structure of the controlsurface is arranged on the end of the first component that faces awayfrom the upper edge. In this way the first component can exhibit a crosssectional profile that is shaped in essence like an omega, and hassufficient design space for housing a second component. Furthermore,this profile exhibits an especially advantageous moment of surfaceinertia for absorbing mechanical flexural or torsional loads.

In a preferred embodiment of the load introducing element of theinvention, the first flange and the first component are constructed fromcommon layers of material in the form of fibrous structures, fiberbraids, composite fiber mats or other similarly constructed layers of afibrous material. As a result, it is possible to minimize the risk ofmechanical damage (resulting, for example, from fastening the flange tothe first component) between the first flange and the first component.

Furthermore, the production of such a component is simplified and is,consequently, more cost effective. Finally even the introduction offorce can be designed so as to be very uniform and continuous betweenthe flange and the first component, so that it is possible to make thewall thickness correspondingly thin.

In an especially preferred load introducing element of the invention,the second component is enveloped (at least in certain areas) by thefirst component. In this way it is also possible to achieve anespecially uniform and continuous transmission of force between at leastone eye of the second component into the first component of the loadintroducing element of the invention. In addition, the free space thatis available in the first component is occupied by the second componentand, thus, additionally reinforces the first component.

It is especially preferred that the second component exhibits a greaterwall thickness in an area that includes the at least the one eye, thanin an area that is enveloped by the first component. In the area thatincludes the at least the one eye, bushings, bolts or the like areusually used by way of a borehole and/or opening, for the purpose oftransferring forces and movements of bearing means to the secondcomponent, so that the mechanical stress of this area is especiallysignificant. In order to prevent the structure of the second componentfrom suffering any damage, the wall thickness in this area must bedimensioned correspondingly. The resulting stresses are distributedoutside this area into the second component, which needs a thinner wallthickness to cope with the loads.

It is especially preferred that the second component exhibits a profilecross section that is essentially U shaped. Such a construction allowsthe second component to be housed very easily in a first component,which has the shape, for example, of an omega, and, moreover, exhibitsadequate design space to house other components. This structure makespossible an especially optimal moment of surface inertia because the legof the U profile is positioned at a distance.

Similarly it is preferred that the load introducing element of theinvention exhibits at least one material layer, the cross section ofwhich is L shaped. Furthermore, said material layer is appliedsimultaneously, at least in certain areas, on at least one element ofthe group, composed of the first component, the second component and thefirst flange. For example, this could be a part of the eye and isapplied from the outside on the second component. In this case the angleis below the flange of the first component. On the other hand, the firstflange could be further reinforced in relation to the first component, astate that could be achieved by laying an L shaped layer of material onthe first flange when affixing to a wall surface of the first component.

Furthermore, it is especially preferred that the load introducingelement of the invention has at least one wall plate that is integratedinto the at least one second component. Such wall plates could be usedto distribute loads in the spanwise direction over both halves of thesecond component and eventually to connect again in a load bearingmanner the load bearing structures of the control surface, which areseparated by the load introducing element of the invention. This couldbe, for example, a front spar or the like. Working on this basis, thereare preferred positions for such wall plates, for example, in the areaof the eyes.

In addition, it is also preferred that the load introducing element ofthe invention has at least one second flange that is alignedsubstantially transversely to the direction of stretch of the loadintroducing element. Such a second flange makes it possible to attachthe load introducing element of the invention to additional load bearingstructures of the control surface—for example, a rear spar and/or anauxiliary spar—that is positioned in the spanwise direction.

In addition, it is preferred that the first component includes aprovision for connecting to a drive armature. The drive armature allowsthe load introducing element of the invention to be deflected in aseparate component, so that the receiving points for the actuators canbe designed in an optimal way, without having to compromise theintegrity of the load introducing element and the points for receivingthe bearing means. Since the load introducing element of the inventiondoes not have unlimited design space inside the control surface, thisapproach offers itself, because the drive armature could be positioned,for example, laterally to the load introducing element of the invention.

Finally it is advantageous if the load introducing element of theinvention is an integral component.

The invention also includes a method for producing such a loadintroducing element, comprising cutting to size preformed fibroussubstructures out of a fibrous material, draping these fibroussubstructures in order to mold the first component, the second componentand the first flange in the form of a single semi-finished product,inserting the semi-finished product into a mold, initiating the matrixmaterial and then curing. This procedure achieves an integral componentin the form of the inventive load introducing element that is limited toa few process steps and, hence, can be carried out at a low cost. Inorder to ensure the dimensional stability of the load introducingelement of the invention, conventional mechanical machining devices canalso be used additionally for subsequent finishing work, the cost ofwhich, however, is unrelated to the cost of machining a solid part to bemilled.

Finally the invention also includes an aircraft or spacecraft which hasat least one control surface with at least one load introducing elementaccording to the invention.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a three dimensional view of an inventive load introducingelement and a drive armature;

FIGS. 2 a and 2 b show is a three dimensional views of two secondcomponents;

FIG. 2 c is a sectional view of a second component in the installedstate;

FIG. 3 is a three dimensional view of a load introducing element,according to the invention;

FIG. 4 a is a three dimensional view of a drive armature;

FIG. 4 b is a three dimensional view of a drive armature rib;

FIG. 4 c is a three dimensional view of a drive armature yoke;

FIG. 4 d is a three dimensional view of an inventive load introducingelement and a drive armature with an additional spar;

FIG. 5 is a schematic view of a mounted control surface with a loadintroducing element, according to the invention;

FIG. 6 is a schematic view of the method according to the invention; and

FIG. 7 depicts an aircraft with a control surface and a load introducingelement according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts an embodiment of a load introducing element 2 accordingto the invention, which includes a first component 4, two first flanges6, a second component 8 (also depicted in FIGS. 2 a and 2 b) with eyes10 and 12 and six second flanges 14, 16, 18, and a drive armature 108with a drive armature rib 20 and a drive armature yoke 22. The firstcomponent 4 of the load introducing element 2 of the invention has anupper surface 26 that is adapted in such a manner that it lies as flushas possible with the inner contour of a control surface, depicted inthis drawing. It is evident that the upper surface 26 of the firstcomponent 4 is arched in a manner analogous to an airfoil of anaircraft. Laterally from the upper surface 26 there are two walls 28,which run substantially parallel to each other and perpendicular to thefirst flanges 6. If the first component 4 were to be cut vertically, thetwo walls 28 would form two legs, which are connected to each other byan upper edge that is adapted to the upper contour of the controlsurface. In this context the upper edge is formed by the cut of theupper surface 26. In the illustrated example the first component 4forms, together with the two first flanges 6, a rigid unit made ofcommon layers of material. This means that on draping the fibrousperforms, a bend 30 is provided, at which the walls 28 are convertedinto one flange 6 in each case. The result is an essentially omegashaped profile contour of the inventive load introducing element 2 inits first component 4 with the first flanges 6.

The first component 4 has a front end 32 and a rear end 34, at which therespective two second flanges 14 and 18 are arranged. The second flanges14 and 18 serve to connect the inventive load introducing element 2 tothe structural components, for example, spars or the like, of thecontrol surface, which is attached to the load introducing element 2.The connection to the structural components can be achieved by adhesivecementing, laminating on, rivets, screws or any other known techniques.

Below the first component 4, and/or enveloped by the same, there is atleast one second component 8, on which are mounted, for example, eyes 10and 12. (See FIGS. 2 a and 2 b.) The eyes 10 and 12 serve to mount, in amoveable manner, the inventive load introducing element 2 on theaircraft or spacecraft, so that the load introducing element 2 of theinvention can traverse a motion path that is defined by the respectivebearing means. A so-called “swing link” is mounted, for example, at theeye 10, and two openings 36, on the front side 32 of the loadintroducing element 2.

In order to perform a desired movement, it is necessary to drive theload introducing element 2 of the invention. For this reason, a drivearmature 108 is arranged on the inventive load introducing element,which can be connected to an actuator by means of the drive armatureyoke 22. For example, the drive armature 108 could be connected by meansof the second flanges 16 and 18 as well as the first flange 6 on theleft side of the load introducing element 2 of the invention.

As FIG. 2 a shows, the omega shaped first component 4 with the firstflanges 6 can have one or more second components 8. In this case thesecond components 8 have a basic U shape, which is open in the downwardsdirection, as shown in FIGS. 2 b and 2 c. This basic shape has, forexample, L shaped material layers 38, which are configured in such a waythat they reinforce the eyes 10 and 12 of the first components 8.Moreover, the bottom side of said material layers can lie flush with thefirst flanges 6. In this way very high strength can be achieved,especially if all of the components of the inventive load introducingelement 2, including the L shaped layers 38 of material, are produced inan integral type of construction with a joint infiltration process and asubsequent joint curing process. Furthermore, as FIG. 2 c shows, thesecond components 8 can exhibit different wall thicknesses in severalareas. Thus, for example, the areas which surround the eye 10 or 12, canbe provided with a relatively large wall thickness, whereas the areas ofthe second components 8 that are surrounded by the first component 4,can be provided with a relatively thin wall thickness.

FIG. 3 shows how the strength of the load introducing element 2 of theinvention can be increased even more. If, for example, the loadintroducing element 2 interrupts one or more structural components ofthe control surface, such as a spar, then the load and/or introductionof force in this area can be bridged by a respective wall plate 40 and42. A first wall plate 40 could be positioned inside a second component8, mounted on the rear end 34, whereas a second wall plate 42 could bemounted more in the direction of the front side 32 of the loadintroducing element 2 of the invention. In the spanwise direction, whichruns substantially transversely to the stretch of the load introducingelement 2, the introduction of force would no longer be interrupted.

FIG. 4 a shows once again a drive armature 108, which consists inessence of two main components, that is, a drive armature rib 20 and adrive armature yoke 22 (FIGS. 4 b and 4 c). The drive armature rib 20exhibits, in the direction of its side faces, a fold 44, which serves asthe flange or the reinforcement, and which could be connected, forexample, to the corresponding second flanges 16 and 18. On a base plate46 there is in the opposite direction to the drive armature rib 20 thedrive armature yoke 22, which has a substantially U shaped profile withvariable height, in which there are two boreholes 48 for receiving andsupporting a driven end of an actuator that is not illustrated. Theforce of the actuator, acting in the openings 48, is transmitted via thebase plate 46 into the drive armature rib 20 and from there via thecorresponding second flanges 16, 18 and eventually 6, into the inventiveload introducing element 2, where it acts in the surrounding controlsurface. In order to improve the force transfer, FIG. 4 d shows anadditional spar 50, which is mounted on the second flanges 18 and thedrive armature rib 20 with its folds 44.

Furthermore, FIG. 5 shows in schematic form, a control surface 52, whichis provided with a load introducing element 2 of the invention and arelated drive armature 108, which is covered in the chosen drawing.Between the openings 36 and the eye 10 there is a “swing link” 54, whichis mounted, for example, on a carriage 56, which is guided on a rail 58.In the rear eye 12 of the load introducing element 2 there is an end ofa connecting member 60 (“rear link”), which is mounted via its endopposite the load introducing element 2, on a body 62, supporting therail 58. In the graphical rendering of this one example, the frontsecond flanges 18 could be attached to a type of front spar 64 or acomparable area of a control surface 52, which is made of fiberreinforced composite materials, the rear second flanges 14 could beattached to a type of rear spar 66, and the central second flanges 16could be attached to an additional structural component (notillustrated) of the control surface 52, so that the load introducingelement 2 of the invention is rigidly integrated into the structure ofthe control surface 52.

FIG. 6 is a flow diagram that shows the method for producing a loadintroducing element 2, according to the invention, which includes thefollowing steps: cutting to size 68 the preformed fibrous substructurescomposed of fibrous material, draping 70 the fibrous substructures tomold the first component, the second component and the first flange inthe form of a single semi-finished product, inserting 72 thesemi-finished product into a mold, injecting 74 the matrix material andthen curing 76. The execution 78 of additional subsequent machining isnecessary as a function of the quality of the production process up tothat point.

Finally FIG. 7 shows an aircraft 80, which includes a plurality ofcontrol surfaces 52, in each of which there are one or more loadintroducing elements 2 of the invention as well as the correspondingdrive armatures 108.

For the sake of completeness it is noted that “comprising” does notexclude any other elements or steps, and “one” does not exclude aplurality. Moreover, features or steps, which have been described withreference to one of the above embodiments, can also be used incombination with other features or steps of other embodiments that aredescribed above. Reference numerals in the claims are not to be regardedas a restriction.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

REFERENCE NUMERALS

-   2 load introducing element-   4 first component-   6 first flange-   8 second component-   10 eye-   12 eye-   14 second flange-   16 second flange-   18 third flange-   20 drive armature rib-   22 drive armature yoke-   26 upper surface-   28 wall-   30 bend-   32 front end of the first component-   34 rear end of the first component-   36 opening-   38 L shaped layer of material-   40 wall plate-   42 wall plate-   44 fold-   46 base plate-   48 borehole-   50 spar-   54 swing link-   56 carriage-   58 rail-   60 connecting member-   62 body-   64 front spar-   66 rear spar-   68 cutting to size-   70 draping-   72 inserting the semi-finished product into the mold-   74 injecting the matrix material-   76 curing-   78 executing the subsequent machining-   80 aircraft-   108 drive armature

1. A load introducing element for a control surface of an aircraft or aspacecraft, said load element comprising: at least one first component;at least one second component; and at least one first flange forconnecting to at least one structure of the control surface; wherein, atleast one surface area of the first component is adapted to an innercontour of the control surface; the second component exhibits at leastone eye for mounting the control surface; and a cross sectional profileof the first component has at least two substantially straight legs,which are connected together on their upper side by means of an upperedge, that is adapted to the contour of the control surface.
 2. The loadintroducing element, as claimed in claim 1, wherein the first flange isarranged on at least one leg on an end of the first component that facesaway from the upper edge.
 3. The load introducing element, as claimed inclaim 1, wherein the first flange and the first component are formed bycommon layers of material.
 4. The load introducing element, as claimedin claim 1, wherein the second component is enveloped at least incertain areas by the first component.
 5. The load introducing element,as claimed in claim 1, wherein the second component has a greater wallthickness in an area comprising at least the one eye than in an areaenveloped by the first component.
 6. The load introducing element, asclaimed in claim 1, wherein the second component has a profile crosssection that is substantially U shaped.
 7. The load introducing element,as claimed in claim 1, further comprising at least one material layerwhich has a cross section that is L shaped, and which is appliedsimultaneously, at least in certain areas, on at least one element ofthe group consisting of the first component, the second component andthe first flange.
 8. The load introducing element, as claimed in claim1, further comprising at least one wall plate, which is integrated intothe at least one second component.
 9. The load introducing element, asclaimed in claim 1, further comprising at least one second flange, whichis aligned substantially transversely to the direction of stretch of theload introducing element for attaching said load introducing element toload bearing structural components of the control surface.
 10. The loadintroducing element, as claimed in claim 1, wherein the first componenthas means for connecting to a drive armature.
 11. The load introducingelement, as claimed in claim 1, wherein: the load introducing element isan integral component; and the first component, the second component,and at least the first flange comprise jointly impregnated and jointlycured pre-finished fibrous substructures.
 12. A drive armature fordriving a load introducing element, as claimed in claim 1, wherein thedrive armature includes means for connecting to the load introducingelement and means for connecting to an actuator.
 13. A method forproducing a load introducing element for a control surface of anaircraft or a spacecraft, said load introducing element comprising atleast one first component, at least one second component and at leastone first flange for connecting to at least one structure of the controlsurface, wherein at least one surface area of the first component has acontour that conforms to an inner contour of the control surface, andwherein the second component has at least one eye for receiving bearingmeans for mounting the control surface, said method comprising: cuttingto size preformed fibrous substructures out of a fibrous material;draping said fibrous substructures to mold the first component, thesecond component and the first flange in the form of a singlesemi-finished product; inserting the semi-finished product into a mold;injecting the matrix material; and curing said semi-finished product toform a finished product.
 14. An aircraft comprising a load introducingelement, as claimed in claim
 1. 15. A spacecraft comprising a loadintroducing element, as claimed in claim
 1. 16. An aircraft exhibitingat least one control surface with at least one load introducing element,as claimed in claim 1.